Net premium drift tracks the running intraday total of bullish minus bearish options premium. Where the options tape shows you individual prints, drift accumulates them into a single measure of net positioning pressure over the session.
Why dollars, not contracts
Counting contracts treats every trade as equal. It is not.
Ten thousand contracts of a far out-of-the-money weekly at $0.03 is $30,000 — lottery tickets. Two hundred contracts of a near-the-money option at $8.00 is $160,000 — real capital with real conviction behind it.
Weighting by premium spent measures how much money is actually behind a direction, which is the thing you wanted to know. Contract counts flatter cheap, noisy flow and understate the trades that matter.
Reading the curves
Each session starts at zero, so you are reading today's flow without yesterday's residue.
Rising bullish drift, flat bearish drift — accumulation. Money is being deployed on the upside and not being faded.
Both rising together — positioning for a move, direction unresolved. Common ahead of catalysts, when both wings get bought.
Divergence from price — the interesting one, below.
Divergences
A divergence is when price and net premium disagree.
Price makes a new high while bullish drift flattens or rolls over: the move is not being funded by fresh positioning. Someone is selling into it, or the buyers have finished. That frequently marks exhaustion.
The inverse — price selling off while bullish drift climbs — suggests the decline is being absorbed. Someone is using the weakness to build.
Divergences are among the more useful things in flow analysis precisely because they are a disagreement between two independent measures. When price and money disagree, one of them is early.
The limits
Direction is inferred. Each print is tagged bullish, bearish, or neutral by comparing it to the prevailing bid and ask. That inference is good but not authoritative — a mid-market print is genuinely ambiguous, and a "bullish" call buy might be a hedge.
Drift is not a timing tool. A divergence can persist for hours or resolve the other way. It tells you the flow underneath the tape has changed character. It does not tell you when price will notice.
Intraday only. The measure resets each session by design. It reads today's pressure, not a multi-day trend.
Use it as a second opinion on the tape, not as a trigger by itself.